Movement Disorders: Phenomenology Separates the Look-Alikes
Describe the movement before diagnosing it
Classify each movement by speed (hypokinetic versus hyperkinetic), rhythm, suppressibility, and relation to rest, posture, and action. Distractibility and suggestibility favor functional movement disorders.
Parkinson disease is asymmetric at onset with rest tremor, bradykinesia, rigidity, and a robust levodopa response. Red flags pointing to atypical parkinsonism include early falls, symmetric onset, poor levodopa response, early dysautonomia, and early dementia. Progressive supranuclear palsy shows vertical supranuclear gaze palsy, early backward falls, and a hummingbird appearance on imaging. Multiple system atrophy shows prominent autonomic failure, with cerebellar features in one subtype and a hot-cross-bun sign on MRI. Corticobasal degeneration shows asymmetric rigidity, apraxia, cortical sensory loss, and alien limb phenomenon. Drug-induced parkinsonism is typically symmetric with no rest tremor and prominent orofacial features.
Tremor. Essential tremor is bilateral, action and postural, frequently with a family history, and improves with propranolol or primidone. Parkinsonian tremor is a resting, pill-rolling tremor.
Hyperkinetic disorders. Huntington disease causes chorea with caudate atrophy and CAG repeat expansion. Sydenham chorea follows streptococcal infection. Tardive dyskinesia appears after dopamine antagonist exposure with choreoathetoid orofacial movements; treatment is discontinuation or VMAT2 inhibitors. Dystonia is sustained abnormal posture; cervical dystonia and blepharospasm respond to botulinum toxin. Wilson disease should be excluded in any young patient with movement disorder plus liver disease or psychiatric symptoms.
Traps: serotonin syndrome (clonus, hyperreflexia, agitation) versus neuroleptic malignant syndrome (rigidity, fever, autonomic instability, elevated creatine kinase, slower onset).
Rule of thumb: symmetric parkinsonism with a history of dopamine blockade is drug-induced until proven otherwise.